A 2°C World? From Probabilities to Possibilities

Last week I was teaching a PhD course on Climate Change Adaptation and Transformations to Sustainability. The 27 students came from diverse backgrounds and were engaged with a variety of research topics. However, all of them were interested in solutions-oriented approaches to climate change and sustainability, including ways to meet the 2°C goal of the Paris Agreement. The question was not so much “is it probable?” but rather, “what does it take to make it possible?”

StatisticsOn the first day of the course, The Guardian published an article with the headline: “Planet has just 5% chance of reaching climate goal, study says.” The article was referring to a study by Raftery et al. in Nature Climate Change, with the title “Less than 2°C warming by 2100 unlikely.” The authors developed a statistically-based forecast of CO2 emissions and temperature change up to 2100 based on the Kaya Identity, which is often used to develop emissions scenarios. The Kaya Identity breaks down future emissions of greenhouse gases into the following factors: population, GDP, energy intensity per unit of GDP and carbon intensity of energy (emissions per unit of energy consumed).

The new study concludes that future policies should target carbon intensity, since policies to reduce GDP per capita seem unlikely. Importantly, the model shows that population increases will not be a major factor in future emissions. Like many other studies, the Raftery et al. article concludes that the 2°C goal is highly unlikely unless emissions reductions occur much faster than in the past. The Guardian’s conclusion was more sobering: there is a “very small chance Earth will avoid warming more than 2°C by century’s end.”

RealityHow do we digest such a devastating conclusion, especially when we understand what is at stake? Critically. In fact, the authors of the study acknowledge that their model does not explicitly take into account future legislation that could change future emissions. They also admit not having taken into account “the possibility that decreasing prices for alternative energy could cause a sudden massive shift to alternative energy” (p. 4). What other aspects of human and social change are overlooked in these scenarios for the future?

What about worldview transformations and the development of a more inclusive social consciousness? As Marilyn Schlitz and her co-authors point out, this leads not just to changes in what people know; it involves changes in how they know what they know, which can change the motivations through which behavior arises. Worldview transformations are linked to paradigm shifts, which can have profound consequences for systems, including economic and social systems. In “The Great Mindshift,” Maya Göpel explores the types of paradigm shifts needed to transform mainstream economics. She reminds us of the importance of “radical imaginaries,” which include holding a vision or belief in what might be possible.

Yes, the relationship between probabilities and possibilities has to be taken seriously. But probabilities are a degree of belief, and since beliefs influence both actions and inactions, we should be cautious about the certainty of our beliefs. Indeed, as Hans Christian Von Baeyer writes in QBism (Quantum Bayesianism), “even certainty is a form of belief” (p. 184).

From Probability to PossibilityThis brings us back to the headline news that our planet has just 5% chance of reaching the 2°C climate goal. Such headlines tend to be much easier to understand than the specific details of the study. The statistics presented in the article were calculated using a Bayesian hierarchical model, fitted using Markov Chain Monte Carlo sampling. This is probably a sound and effective way of modeling the Kaya Identity with all of its assumptions, since Bayesian models update a sequence of data as new information becomes available.

But does the model capture how the consequences of climate change impacts, including how they might influence future policies and practices, and the full potential for radical changes in society? Does the model account for increasing reflexivity and a growing awareness that humans can transform systems to reduce or avoid risk?

Does it recognize the full range of solutions associated with mitigation? This includes the potential to reduce food waste, to increase plant-rich diets and to educate girls – some of the many solutions discussed in Paul Hawken’s recent book Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming. As Hawken explained in a recent interview with Future Earth, the project was developed to see if it was possible to draw down atmospheric CO2 within 30 years, using existing practices, techniques and technologies. Realizing this vision recognizes the possibilities for people to deliberately transform themselves, their systems, and their futures – for the better.

People and ParadigmsIn Understanding Beliefs, Nils J. Nilsson (2014, p. 66) reminds us that we should not confuse our models of reality with reality itself: “Using our model-building apparatus and informed by our perceptions, we can only say things about reality. We can never say what it is. And, most importantly, what we say about it is always subject to revision.” This means that it is important to use models with full awareness of the assumptions, beliefs and perceptions that are embedded in them — including how they are changing over time.

Perceptions are changing, paradigms are changing, and people are changing. This may help explain why there is such fear in the world, and why worldviews are being defended, often with a vengeance. Sure, a Bayesian hierarchical model tells us a lot about the relationship between population, GDP, energy intensity of energy and carbon dioxide emissions. And the news about uncertainties related to greenhouse gas emissions monitoring and accounting is alarming. But after spending a week with a group of bright and critically engaged PhD students, I am convinced that people and paradigms will turn out to be the real solution to climate change.